Conventional operation of a tank type water heater is well known. Water in the water heater tank is typically maintained at a relatively high temperature (e.g., 140° F.) by a simple control system that runs the heater element when the tank temperature is too low and turns the heater element off when the tank temperature is high enough. This arrangement can lead to relatively high standby losses, because the water tank temperature is always high, even during times when little or no hot water is needed, e.g., while house occupants are away or asleep.
Efforts have been made to alleviate this issue by controlling the water heater to account for demand, such that the heating element can be turned off in periods when there is no demand. U.S. Pat. No. 8,461,493 and US 2013/0299600 are representative examples of this approach. In these references, hot water demand is measured by monitoring the output from the water heater.